This invention relates to a fluorosilicone terpolymeric fluid which, at a high viscosity, can be used as a self-bleed additive for fluorosilicone heat curable rubber compositions. More particularly, the present invention relates to a self-bleed additive which acts as a release agent after post baking a fluorosilicone heat curable rubber composition. At a low viscosity, the fluid can be used as an additive for personal care products to enhance the water and oil repellency of the products.
Elastomeric heat curable rubber (HCR) compositions derived from fluorosilicone high molecular weight (HMW) polymers are utilized in applications which require good solvent resistance and good mechanical properties. The cured compounds are often used in applications where a molded part must be inserted into a metal appliance prior to utilization of the molded part. A raw material user, or fabricator, usually works with uncured compositions, injecting them into molds where they are press-cured to form a molded part. Occasionally, the fabricator requires a lubricated surface on a cured part to facilitate insertion of the part into a mechanical appliance of some kind. Most processes avoid the use of externally applied lubricants and instead preferably use compounds which release a film of lubricant to the cured surface after the curing process (press cure and post bake). Compounds which incorporate lubricants and release them after molding are called self-bleed compounds.
It is desired to produce a fluorosilicone heat curable rubber composition which exhibits a self-bleed after post-baking. Such a composition could be used to provide a molded gasket or seal which would exhibit lubricant on its outer surface and would thus easily slip over or into a metal part/appliance despite a tight fit. For example, it is desired to provide a self-bleeding insulator for a spark plug which can easily slip over the plug yet provide a tight fit to the plug.
The fabricator also prefers a self-bleed additive which does not liberate excess volatiles in the post-bake oven. Such volatiles may be environmentally unacceptable and dangerous to the user.
Self-bleed compounds are made by incorporating a non-compatible fluid into an HCR composition in an amount sufficient to effect a "bleed". The utilization of phenyl-containing silicones in this application is well known for polydimethylsiloxane (PDMS). Improving the efficacy of the self-bleed of PDMS by adding fluorosilicone containing fluids is described in European patent application no. 369,255.
The utilization of a phenyl-containing copolymeric fluids as a bleed agent for fluorosilicone compositions has been described in U.S. Pat. No. 4,742,101 to Yoshida. Yoshida discloses that copolymeric fluids where the phenyl group varied over the range of 70/30-25/75 are most effective.
A typical bleed agent formulation disclosed in Yoshida is: ##STR1## wherein some of the R' groups are phenyl groups and some are methyl groups. Two typical examples are: ##STR2## where x=1 or 3, and Ph is a phenyl group.
When used in conjunction with diphenyl diol filler treating agents, these fluids self-bleed after the composition is cured at 165.degree. C. for 10 minutes. In Yoshida, all of the bleeds are described as being good after press cure. However, Yoshida provides no information about the self-bleed performance of the compositions after post bake.
The type of self bleed preferred on the post-bake samples is one which, when handled, allows a user to know there is a lubricant on the surface and wherein the lubricant is transferred to the hands.
One problem with the Yoshida agents is that processability is adversely affected by the addition of phenyl-containing copolymer fluids. These fluids tend to liver-up the material during addition of the fluid to material on a mill. The term "liver-up" has become well known to those of skill in the art and refers to the condition of stock material when it becomes too wet and either becomes too difficult to apply on a mill or falls off the mill. To minimize this problem, it is necessary to add raw fumed silica to soak up the fluid in the composition. The utilization of the fumed silica offsets a decrease in Durometer which often occurs with the addition of the self-bleed fluids.
Fluorosilicone HCR compositions prepared with known phenyl-containing silicone fluids do not perform very well. The bleed of the compositions was erratic. Testing done on compositions utilizing diphenyl diol as described by Yoshida improved the performance of the phenyl-containing silicone fluids in self-bleed after press cure; however, no improvement in performance was exhibited after post bake.
Some of the same desired properties of a self-bleed additive are also desirable in personal care products such as skin creams and lotions, hair conditioners, lipsticks, antiperspirants and deodorants. It is particularly desirable that these products exhibit excellent water and oil repellency and a resistance to washing off.